In the past, various systems have been presented to utilize naturally occurring sources of energy to heat or cool an enclosed structure, such as a house or office building. More often than not, these systems have been dependent upon solar energy as their sole source of energy input. These systems have not achieved widespread usage due to their inability to achieve consistent heating or cooling due to the unpredictability of the solar energy source.
Systems have also been put forth which introduce means to store heat or "cold" for use at a time when there was no solar energy input. However, these systems also suffer drawbacks, since the storage means becomes prohibitively large if capable of providing for several days of energy without solar input. Also, these systems have typically used a single closed loop cycle with a single fluid in the loop for both heating and cooling. This has resulted in inefficient heating and cooling since the fluid utilized is usually a compromise between a fluid which is capable of maximum efficient heating and a fluid which exhibits similar properties for cooling.